Method of hardening iron and steel



Patented Oct. 9, 1934 UNITED STATES PATENT OFFICE No Drawing. Application December 2, 1932,

Serial No. 645,413. In Germany December 9, 1931 -2 Claims.

The subject of the invention is a process for hardening iron and steel, which difiers from the known similar methods essentially and advantageously in that itsucceeds in imparting to the steel an unusually high degree of hardness in a simple and comparatively short treatment whilst obtaining great core tenacity. Thereby the tedious and expensive case hardening is rendered superfluous in very many cases.

As is known, steel is hardened, bybeing heated after the forming treatment and quenched by being dipped into a cold fluid. Frequently it is previously subjected to a so called carbonization. As a quenching agent, for the most part, water is employed either alone or with additions of salts, acids, alkalis or other substances. For

quenching alloyed steels, rape seed oils are mainly used.

In order to incorporate more carbon in theimpart to it a greater hardsubstances, often subjected 'to an intermediateheating to red heat, and finally heatedagain and quenched.

Applicant has now found that high degrees of hardness can be imparted to the steel in a considerably simplified and more economical manner if it is heated to red heat in a carbon dioxide containing atmosphere and then dipped in a bath which contains resins or resin soaps together with carboncontaining and if desired nitrogen-containing substances, dissolved or suspended in oils or'fats.

The action of this hardening means can be further increased if metal compounds in the form of resin bonyls and the like are added to it.

Solutions or suspensions of resins, such as colophon together with resin acid salts, such to the so called case hardacid metals, metal formates, car-- as resin.- acid alkali in oils of high flash point such for example as linseed oil have been found to be particularly suitable for use.

As nitrogen and carbon containing compounds, urea, formates and the like can be employed. Also numerous other organic compounds can be employed. It is important however that they contain no water of crystallization.

Example The articles to be hardened are heated in a carbon dioxide-containing atmosphere .to 850-950" and then dipped in a hardening bath and allowed to cool completely. in this. This hardening bath advantageously consists of 100 parts by weight of linseed oil in which 12 parts by weight of colophony are dissolved.v The s'olution also contains 3 parts by weight of resin acid potassium and 3 parts by weightzrof nickel formate; instead of or in addition to the nickel formate, also 7.5 parts by weight of urea can be added. The steel or steel articles treated in this hardening bath are then heated up again to red heat and quenched in water.

It appears that the metal compounds act upon the articles to be hardened by catalytical properties.

I claim. 4

1. A method of hardening iron and steel, ,comprising heating the articles to be hardened to red heat in an atmosphere containing carbon dioxide, quenching the articles in a bath of linseed oil in which colophony, resin acid potassium and nickel fo'rmate have been dissolved, reheating to 

